Stereoscopic systems operate by presenting two distinct images to a viewer, a first image being presented to the right eye and a second image being presented to the left eye. Polarization or spectral-division methods may be used to separate the two images. The right-eye and left-eye images may be coded with orthogonal polarizations at an image source, and viewer polarization optics may allow light of orthogonal polarization states to be passed onto different eyes, thereby creating the perception of 3D images.
Some conventional techniques for modulating polarization for a stereoscopic display are described by Lipton in commonly-owned U.S. Pat. No. 6,975,345 (“Lipton '345”), and by Byatt in U.S. Pat. No. 4,281,341 (“Byatt '341”), both of which are incorporated herein by reference in their entirety. In general, Lipton '345 describes a polarizing modulator for use in an electronic stereoscopic display system having a sequentially scanning display that includes a plurality of liquid crystal (LC) segments arranged contiguously in a direction of the sequential scan. The liquid crystal material used in each polarization modulation segment has its phase shift tuned in an attempt to minimize the perception of a visible line between segments. Byatt '341 describes a stereoscopic television system that employs a switchable optical polarizer to alternately form images corresponding to the left and right eyes on a television camera. A corresponding switchable polarizer, which comprises a liquid crystal cell containing a thin layer of twisted nematic liquid crystal material, is used in combination with a display device to produce alternating images that are vertically or horizontally polarized. The switchable polarizer associated with the display device is switched in synchronism with the operation of the switchable polarizer associated with the camera.
Unfortunately, despite prior attempts at solutions, the boundaries between the horizontally striped electrodes of an active retarder stereoscopic display are often visible as the LC molecules twist under the influence of in-plane electric fields at the boundary between adjacent segments. Accordingly, what is needed is a technique for avoiding such twisting and thus reducing the visibility of segment boundaries.